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To the members of The South African Institute of Mining and Metallurgy I have audited the annual financial statements of The South African Institute of Mining and Metallurgy set out on pages 641 to 644 for the year ended 30 June 2006. These annual financial statements are the responsibility of the Institute?s Council members. My responsibility is to express an opinion on these annual financial statements based on my audit. Scope I conducted my audit in accordance with International Standards on Auditing. Those standards require that I plan and perform the audit to obtain reasonable assurance about whether the annual financial statements are free of material misstatement. An audit includes: ?examining, on a test basis, evidence supporting the amounts and disclosures in the annual financial statements, ?assessing the accounting policies used and significant estimates made by management, and ?evaluating the overall financial statement presentation. I believe that my audit provides a reasonable basis for my opinion. Audit opinion In my opinion, the annual financial statements present fairly, in all material respects, the financial position of the Institute at 30 June 2006 and the results of its operations and cash flows for the year then ended in accordance with generally accepted accounting practice appropriate to the Institute. Supplementary information The supplementary schedule does not form part of the annual financial statements and is presented as additional information. I have not audited this schedule and accordingly do not express an opinion on it.

Jan 1, 2006

By M. K. Matthews

The use of backfill has important environmental control implications which, although frequently overlooked, can be both beneficial and problematical. Where backfill is widely used, the reduction in stope heat load and improved air utilization influence the overall mine ventilation and refrigeration requirements significantly. A programme of work examining in detail all the environmental consequences of backfilling is currently underway at the Environmental Engineering Laboratory of the Research Organization of the Chamber of Mines. This paper gives an overview of the work and presents some findings. In so doing, the environmental implications to be considered when backfilling are highlighted.

Jan 1, 1988

Determination of mineral composition is of significant importance for the mineral sands industry as this information is required for orebody evaluation, the control of mineral processing plants and the determination of product quality. Mineral processing is made more difficult by the presence of pseudorutile, leucoxene, altered-ilmenite and particle inclusions. The paper investigates the properties of such elements from a single product stream using an MLA approach.

Jan 1, 2007

By J. Abdollahisharif

Optimal cut-off grade is one of the most critical parameters in open-pit mine design because it defines the ore and waste and thus determines the maximum net present value possible from the mining operation. Although the algorithm presented by Lane (Choosing the optimum cut-off grade. Colorado school of Mines Quarterly, vol. 59, no. 4, 1964. pp. 811-829) is the most common one in the literature, it does assume constant capacities of the mine, processing, and refinery. In this paper, Lane's original algorithm has been modified to consider variable processing capacities in order to determine the optimal cut-off grade in open-pit mines. The new algorithm proposed here is compared to both Lane's original algorithm and to a previous modification that incorporated rehabilitation costs into the cut-off grade estimation. The algorithm proposed here that permits variable processing capacities is shown to be superior for the determination of optimal cut-off grade to both these previous versions. In addition, a computer-based program was developed in Microsoft Office Excel© to calculate the optimal cut-off grade as proposed here.

Jan 1, 2012

A method, based on the macroscopic population balance equation allowing the dynamic simulation of a multistage adsorption plant given an arbitrary rate expression, is described. The partial differential equations resulting from this method are simplified using the method of characteristics. The simplified equations can then be solved using standard ODE integration techniques. The procedure is illustrated by means of data typical of a CIP application. Requirements for data structures which allow the incorporation of the carbon-in-pulp (CIP) model (and other unit models) into a general metallurgical simulator are described. Based on these considerations, it is concluded that more generality in the description of distributed quantities such as loading and particle size is provided by the use of mass density at fixed class boundaries, rather than discrete masses within fixed classes as has hitherto been used by ore-dressing simulators.

Jan 1, 1987

By L. A. Abichequer

ROM grade variability is one of the most important factors influencing plant product recovery. Due to the influence of grade variability on mine profits, it is deemed important to guarantee a proper homogenization of the ore through a well-planned blending and homogenization pile system from which the ore is reclaimed at an acceptable grade fluctuation. This study tests geostatistical simulation efficiency in predicting in situ grade variability. The methodology is illustrated using a data-set from a large phosphate mine in central Brazil. Additionally, real data obtained at the mine site during January and February 2007 were used to derive the actual grades of each pile formed during this period. Each pile was formed by a selection of blocks within a dig line and these lines mined along the year 2007 were also made available. Given the real grades, it was possible to reconciliate and validate the results predicted by the proposed methodology. The main outcome of this study is the opportunity to check the geostatistical simulation as a tool to quantify the variability of the homogenization system.

Jan 1, 2009

By O. Bazhko

Regular analysis of different streams is important for the control of hydrometallurgical processes. Various physical and physical-chemical methods are applied for this purpose. Many modern methods require costly equipment and are subject to interferences. Therefore, redoxtitration methods remain of interest. The use of different types of oxidizing and reducing agents as well as redox indicators enables many cations and anions to be rapidly and accurately analysed. Sometimes redox titrations require the prior preparation and addition of masking agents. Selective, sensitive and low-cost methods of redoxtitration of copper and SO2 in plant conditions are described.

Jan 1, 2009

By J. E. Chilton

No regular monitoring of methane is required in areas of gassy coal mines outby the mining face. Methane ignitions that have occurred in mine outby areas indicate the need to provide better protection to workers. Handheld methane monitors are now used by some miners to make periodic measurements of methane at the working face. The IYONI II gas detector which is incorporated into a miner’s cap lamp and worn on a miner’s helmet can continuously provide an alarm signal whenever methane levels exceed a set level. Tests were conducted to evaluate the performance characteristics of this methane detector by measuring response times with methane gas supplied through a calibration fixture or adaptor. Other response time tests were performed with the detector in an environmental test box. Performance was also evaluated in a full scale test gallery where face methane emission and underground ventilation were simulated. Procedures for calibration by response time measurement of the IYONI II detector have been developed. In limited testing, the IYONI II detector was found to reliably detect the presence of 1 percent by volume methane.

Jan 1, 2003

By H. Jeram

The ilmenite, rutile and zircon processes of the mineral separation plant generate tailing streams, which still contain valuable mineral. This is due to a combination of factors, which include separator equipment efficiency, particle size effects and inefficient operating practices (equipment overloading, blockage, etc.). Recent developments by metallurgical equipment suppliers have led to increased mineral separator performance enabling recovery of previously lost valuable mineral. Mineralogical studies were conducted using QEM*SEM and MLA techniques to identify and quantify gangue mineral species and determine mineral association. Laboratory and pilot-scale test work was then conducted to develop suitable process flowsheets for the recovery of ilmenite, rutile and zircon from current and stockpiled tailings.

Jan 1, 2007

By P. R. Janisch

This paper reviews the sources, production, and technology of gold in South Africa. First of al it details the geographical distribution of gold-bearing materials, together with the mineralogy and distribution of gold within those materials. It goes on to the geological origins, and to the discovery and early exploitation, of the gold deposits. The laws relating to the mining and disposal of the metal are explained, after which an outline is given of gold exploration, processing, and refining. The economics of gold production are discussed briefly, and it is concluded that, although present expertise in the financial and technological aspects of a gold-mining venture have largely reduced the risks involved, one severe risk remains: that the rate of cost inflation will not be matched by the rate of escalation in the gold price.

Jan 1, 1986

By P. Otto, G. Borm, Th. Dickmann, F. Amberg, R. Giese

Based on many years experience, the well proven Swiss Tunnel Seismic Prediction System TSP has been substantially augmented for online geological prognosis in underground construction. In its latest version, the Integrated Seismic Imaging System ISIS provides high resolution seismic images of the rock mass around a tunnel face via an array of standard anchor rods. These rods contain 3D-geophones at their tips and can be readily installed during excavation work. A further innovative component of the system is the newly developed high-power repetitive source for application in hard rock: a pneumatic hammer with laser triggering to be mounted on construction machinery. A user-friendly software package permits online data acquisition and processing, 3D-visualization, and a first geological interpretation. Tomographic images of compressional and shear wave velocity fields at fault zones in metamorphic rock of the Gotthard Base Tunnel in the Central Alps are presented. Das langjährig bewährte Schweizer Tunnelseismische Vorauserkundungssystem TSP wurde inzwischen wesentlich weiterentwickelt. In seiner neuen Version, dem Integrierten Seismischen Imaging System ISIS, ermöglicht es hochauflösende seismische Abbildungen des Gebirges im Vorfeld und Umfeld einer Tunnelauffahrung mit Hilfe einer Anordnung von Felsankern, die an ihren Spitzen 3-Komponenten-Geophone enthalten. Eine weitere Neuerung von ISIS ist die pneumatische Hochleistungs-Impulsquelle mit Laser-Triggering. Eine benutzerfreundliche, interaktive Software ermöglicht die online Datenerfassung und -auswertung, 3D-Visualisierung und eine erste geologische Interpretation. Tomografische Abbildungen von Kompressions- und Scherwellengeschwindigkeitsfeldern an Störungszonen in metamorphem Gestein des Gotthard-Basistunnels werden gezeigt. Basé sur de nombreuses années d’expérience, le système suisse, bien établit, de reconnaissance sismique à l’avancement des tunnels (système TSP), a été sensiblement amélioré pour obtenir une prévision géologique en temps réel durant l’avancement de travaux souterrains. Sa dernière version, le Système Intégré d’Imagerie Sismique (ISIS), fournit des images sismiques haute-résolution du massif rocheux à l’avant d’un tunnel grâce à un réseau de tiges d’ancrage standard. Ces tiges, équipées à leur extrémité de géophones 3 composantes, s’installent très aisément durant les travaux d’excavation habituels. Le élément d’innovation récente concern le nouvelle source très répétitive et de forte puissance pour les applications aux roches dures: un marteau pneumatique déclenché par un système à laser. Un ensemble de programmes informatiques convivial permet l’acquisition et le traitement en temps réel des signaux et produit une vue 3D ainsi qu’une première interprétation géologique. Nous présenterons des images de réflexion d’ondes de compression et de cisaillement ainsi que des inversions tomographiques de zones de faille dans des terrains métamorphiques obtenues à l’occasion du creusement du tunnel de base du Gothard, dans les alpes centrales.

Jan 1, 2003

By SAIMM SAIMM

To the members of The South African Institute of Mining and Metallurgy We have audited the annual financial statements of The South African Institute of Mining and Metallurgy set out on pages 575 to 586 for the year ended 30 June 2005. These financial statements are the responsibility of the Institute?s Council. Our responsibility is to express an opinion on these financial statements based on our audit. Scope We have conducted our audit in accordance with International Standards on Auditing. Those standards require that we plan and perform the audit to obtain reasonable assurance about whether the financial statements are free of material misstatement. An audit includes: examining, on a test basis, evidence supporting the amounts and disclosures in the financial statements, assessing the accounting principles used and significant estimates made by management, and evaluating the overall financial statement presentation. We believe that our audit provides a reasonable basis for our opinion. Audit opinion In our opinion, the financial statements fairly present, in all material respects, the financial position of the Institute at 30 June 2005 and the results of its operations and cash flows for the year then ended in accordance with South African Statements of Generally Accepted Accounting Practice.

Jan 1, 2005

By L. I. Boshoff, S. Gracie

This paper discusses pilot and laboratory-scale metallurgical test work conducted on bulk samples from a low grade heavy mineral deposit and provides an overview of basic practical metallurgical techniques applied to ascertain the suitability of existing production plants to process material from this orebody. Previous investigations have shown this specific orebody to be more challenging in terms of mineral beneficiation as it has a high gangue mineral content. Test work was conducted on targeted stratigraphic units based on lithology and assay results to enable identification of the stratigraphic units portraying quality issues. Unit specific metallurgical pilot work has never been conducted on any of the RBM orebodies and is a new field currently being explored. During this investigation focus was placed on potential quality and yield issues for ilmenite product, with particular reference to CaO quality. A basic evaluation of zircon and rutile separability was also conducted. The test work was conducted using a comparative baseline methodology with metallurgical test work methods specifically aiming at mimicking the existing production plant as closely as possible. This enabled not only the likely metallurgical performance to be assessed but also indicated whether current plant design would be suitable to process the low grade ore types into products of acceptable quality at acceptable yields. The methods and findings discussed in this paper indicate that although there is considerable variation between different units, a blended feed can be successfully processed. With unit specific metallurgical data applied to the existing geological block model, expected yields and recoveries using current plant designs could be predicted.

Jan 1, 2007

By M. F. Handley

This paper covers in situ stresses in the Earth?s crust prior to any man-made disturbances, such as mining. It introduces the Southern African Stress Database, which contains primitive stress measurements obtained from locations spread all over southern Africa. The measured stress data shows large variability without any visible trends, except a relationship with increasing depth. The stress database is reviewed briefly, establishing means to measure the variability or dispersion in the measurements, and showing that the dispersion is not as much a result of experimental error as it is a feature of primitive stress. The paper demonstrates from the beginning that the state of stress in rock is highly variable, but that there are well-defined maximum and minimum limits to all the stress components in rock. Formal error analysis is introduced to check the consistency of the database and to separate out a database of consistent stress measurements for use in a primitive stress model. The aim is to provide a picture of primitive crustal stress based on objective stress measurements together with interpretations of how the primitive stress can be affected by the five main influences; namely, depth, rock mass properties, tectonism, isostacy, and erosion. Four elementary models for primitive stress are introduced and compared with the measured data. It is quite clear that none of the elementary models is sufficient to describe the data. In the absence of a better model, this paper suggests a generic model based on the Hoek-Brown failure criterion and the consistent stress database, since it incorporates the variability in the stress tensor that is likely to be encountered underground all over southern Africa. Rock engineers should take every opportunity to obtain local primitive stress data at every mining operation and civil engineering project, and to adjust the proposed model accordingly Keywords primitive stress, Southern African Stress Database, error analysis, generic primitive stress model.

Jun 1, 2013

By P. Jordan

The practice of ilmenite smelting in electric arc furnaces has been researched and published over the last few decades. An issue that has not been addressed is the understanding of the properties of ilmenite smelting reductants, and linking these properties to the subsequent smelting behaviour in the furnace. The reduction mechanism of ilmenite smelting is not fully understood, but it is believed that the Boudouard reaction plays a role. This paper investigates the behaviour of a number of reductants when reacted with CO2 at different temperatures. Keywords Boudouard reaction, carbon reactivity, reductants, ilmenite smelting.

Jan 1, 2011

By Sönke Schmachtel

Several possible physico-chemical properties of composite electrodes for oxygen evolution are presented to describe experimental data for which a mathematical model had been developed. On this basis, local electrical and electrochemical properties of a composite electrode were investigated with conductive atomic force microscopy (CAFM) and scanning electrochemical microscopy (SECM). It could be shown by CAFM measurement that the boundary between matrix and catalyst particles seemed to have special advantageous electrical properties. The SECM measurements showed the presence of mass transport phenomena with increased surface concentrations, whilst the thickness of the Nernst diffusion layer was very small. An intermediate was detected and assigned to be hydrogen peroxide. From all species involved in the oxygen evolution reaction (H2O2, H+ and O2), it was concluded that local active spots exist on the electrode on which hydrogen peroxide reacts to oxygen and protons. A two?step two-material process was suggested to explain the whole oxygen evolution mechanism.

Jan 1, 2008

By B. P. Watson

The Bushveld platinum group metal deposits in South Africa are the largest in the world. These deposits occur as two distinct stratiform tabular ore bodies and strike for many hundreds of kilometres. Mining is extensive, with depths ranging from close-to-surface to 2300 m. The mining method is a variation of planar open stoping. Crush pillars are widely used to support the open stopes. These pillars are designed to fail and the residual strength provides the required support resistance to stabilize the stoping excavations. This paper describes the in situ measurement, of stress within a Merensky pillar from Impala Platinum. These measurements were used to derive a stress-strain curve that includes pre and post failure behaviour. 2D FLAC modelling, with strain softening, was done to investigate how damage expands into the hanging- and/or footwall. Although the so-called ?squat? effect is always present, the modelling suggests that it does not dominate the pillar system behaviour at larger width to height ratios. Punching of the pillar into the hanging- and/or footwall increasingly controls the pillar system behaviour with larger width to height ratios. The paper investigates the behaviour of a system that incorporates the immediate hanging- and footwall, as well as the pillar itself.

Jan 1, 2009

Acid heap leaching has been extensively applied to the processing of copper oxide ores, with recovery of copper by solvent extraction and electrowinning. Heap leaching has also been extended to the treatment of secondary sulphide copper ores, where oxidative conditions are generated in aerated heaps by the bacterially-assisted oxidation of ferrous iron to ferric iron. The treatment of low-grade chalcopyrite ores has recently been the focus of research, with Mintek playing a prominent role. When processing chalcopyrite ores, more complex column test work is performed, which incorporates the prediction and simulation of temperature behaviour in pyrite-containing heaps. Mintek has devised a trade-marked column leaching apparatus (SmartColumn?) for the simulation of the natural temperature profile development in pyrite-containing heaps. As heap leach applications are becoming more complex, the parameters that need to be built into the design and operation of heap leach plants are growing in number, and the amount of data to be collected and processed, and the number of decisions to be taken daily, are also increasing. Mintek has therefore developed the HeapStar® administrative advisory software, as a guidance system to ensure that the correct protocols are implemented at various stages of the leach cycle.

Jan 1, 2012

By A. Karadogan

Decision making can be defined as the selection process of the best routes from the alternatives in order to achieve a goal, and mostly involves uncertainty. Additionally, mostly qualitative variables (weak rock, massive ore deposit, etc.) are in question. Mine planning engineers often use their intuition and experience indecision making. As fuzzy set theory has been used since 1970, these uncertainties are easily evaluated in the decision-making process. Real world study is decision making under vague constraints of different importance, involving uncertain data (qualitative variables), where compromises between antagonistic criteria are allowed. This paper presents a new approach in the selection of an underground mining method based on fuzzy set theory for the Ciftalan Lignite Site located close to Istanbul in Turkey. The physical parameters such as geology and the geotechnical properties of ore, hanging and foot wall, economic effects, environmental effects, are established with field and laboratory tests together with the determination of other qualitative variables. Meanwhile, some qualitative variables dealing with the matter was described according to the view of a number of experts. Then fuzzy set theory is applied to these parameters, considering the available underground methods in order to choose the proper method. At the end of the evaluations, the room and pillar method with filling was determined as the most suitable method for the test site. Keywords: Decision making, fuzzy set theory, underground, mining, method selection

Jan 1, 2008

By A. Montini

The problems encountered in the design of control systems for milling cir- cuits when the model of the system and the model parameters are uncertain are discussed. Considering these uncertainty factors has led to the development of a technique that gives a quantitative assessment of real system stability, reveals the trade-offs between performance and stability and helps the designer in deciding what level of model complexity to use in the controller design. Furthermore, it allows for on- or off-line optimization of the milling circuit performance as it provides the base for the design of a controller which is stable over the plant operating range.

Jan 1, 1987